OLDS 88 STALLS AFTER 20 MIN, 104K MILES

1989 Oldsmobile Delta 88 • 104,000 miles

Have a 1989 Olds 88, with 3.8L engine and 104K miles. Car runs great however after 20min of driving will stall, then becomes hard to run again, or if running then stalls again. Has following codes stored: 41, 42, 44. The following have been replaced: air filter, fuel filter, spark plugs, cam sensor, crank sensor, and ignition module. Car has new exhaust put on which has resonator inplace of cat-converter. Car had stalling problem before new exhaust put on. Will gladly 'donate' if advise leading to fixing this problem is given! Thanks.

CAUTION: Some vehicles may have different wire colors. See TSB No. 89-6E-9
To set a Code 42 the following conditions must occur: ? Engine speed greater than 600 RPM with no EST pulse for 100 -200 milliseconds (open or grounded circuit No. 423).
? OR: ECM commanding bypass mode (open or grounded circuit No. 424).
NOTE: Test numbers refer to test numbers on diagnostic chart.
1.
Checks to see if ECM recognizes a problem. If it doesn't set Code 42 at this point, it is an intermittent problem and could be due to a loose connection.
With the ECM disconnected, the ohmmeter should be reading less than 200 ohms, which is the normal resistance of the EST circuit through the ignition module. A higher resistance would
indicate a fault in circuit No. 423, a poor ignition module connection, or a faulty ignition module. If test light was on when connected from 12 volts to ECM harness terminal "BC7", either circuit
No. 423 is shorted to ground, or the ignition module is faulty.
Checks to see if ignition module switches when the bypass circuit is energized by 12 volts through the test light. If the ignition module actually switches, the ohmmeter reading should shift to
greater than 6000 ohms.
Disconnecting the ignition module should make the ohmmeter read as if it were monitoring an open circuit (infinite reading). Otherwise, circuit No. 423 is shorted to ground.
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Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
? Poor Connection - Inspect ECM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and
damaged harness.
? Intermittent - If connections and harness checks out okay, monitor a digital voltmeter connected from the affected terminal to ground while moving related connectors and wiring harness. If the
failure is induced, the voltage reading will change.
CAUTION: Some vehicles may have different wire colors. See TSB No. 89-6E-9
Fig. 103: Code 42: EST Ignition Ckt Diag (3.3L A Body) Some vehicles may have different wire colors. See TSB No. 89-6E-9
Fig. 104: Code 42: EST Ignition Ckt Diag (3.8L C/H Body) Some vehicles may have different wire

Code 44 is set when the oxygen sensor signal voltage on circuit No. 412 remains less than.25 volt for up to 4.5 minutes and the system is operating in "closed loop".
NOTE: Test numbers refer to test numbers on diagnostic chart.
1.
Running the engine at 1200 RPM will keep the O2 sensor hot so an accurate display of voltage is maintained. Opening the sensor wire should result in a voltage display of.35-.55 volt. If the
display is still fixed at less than.35 volt, the fault is a short to ground in circuit No. 412 or a faulty ECM.
Diagnostic Aids

Using the "Scan" tester, observe block learn values at different RPM and airflow conditions. "Scan" tester also displays block cells, so the block learn values can be checked in each cell to determine when
Code 44 may have been set. If the conditions for Code 44 exist, the block learn values will be around 150. Check the following: ? Oxygen sensor pigtail may be mispositioned and contacting the exhaust manifold. ? Check for intermittent ground in wire between connector and sensor.
? A Mass Airflow (MAF) sensor output that causes the ECM to sense a lower than normal airflow will cause the system to go lean. Disconnect the MAF sensor and if the lean condition is gone,
replace the MAF sensor.
? Perform injector balance test, refer to CHART C2A - INJECTOR BALANCE TEST below in this article.
? Water, even in small amounts, near the intank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set Code 44.
? System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm problem. See fuel system
diagnosis CHART A7: FUEL PRESSURE TEST.
? If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust across the oxygen sensor. Vacuum or crankcase leaks can cause a lean condition.
? If all of the above checks are okay, replace oxygen sensor.
Fig. 110: Code 44: Lean Exhaust Indication Ckt Diag (3.3L A/N Body)
Fig. 111: Code 44: Lean Exhaust Indication Ckt Diag (3.8L C/H Body)
Fig. 112: Code 44: Lean Exhaust Indication Flow Chart